Temperature measuring apparatus



Aprilv l, 1941. l A, E. KRQGH 2,237,036

TEMPERATURE MEASURING APPARATUS original Filed June 12, 1935 2sheets-sheet 1 INVENTOR." ANKgR EKROGH t CAL Pll 1, 1941 A. E. KROGH2,237.036

TEMPERATURE MEASURING APPARATUS Original Filed June l2, 1955 2Sheets-Sheet 2 INVENToR. ANKER E. KRoGH avg-iq h Patented Apr. l, 1941TEMPERATURE MEAsUmNG APPARATUS zaten i Anker E. mogli, Philadelphia,ra., assignor :o The Brown Instrument Company, Philadelphia, Pa.,

a corporation of Pennsylvania.

Continuation of application Serial No. 26,130, June 12, 1935. Thisapplication May 20, 1937,

Serial No. 143,815

Claims.

The general object of the present invention is to provideimprovedcontrol apparatus especially adapted for use in the practice ofthe method of measurement and control of metallurgical furnacesdisclosed in my prior patent applica# tion Serial Number 26,130 led June12, 1935, of which this application is a continuation. but comprising`novel features of construction and arrangement not restricted to suchuse.

My novel method of control is characterized primarily by the fact thatthe combustion in the furnace is controlled by and in accordance withthe heat potential in the combustion chamber adjacent a highlyheatedportion of the combustion chamber wall. In an open hearth furnace usedfor annealing and other'metallurgical purposes, the roof of the heatingchamber above the furnace hearth, is a portionof the furnace highlyheatedv in normal operation, and I have found that in the operationofsuch a furnace it is highly advantageous to regulate combustion in thefurnace so as to maintain thel heat potential against the roof at anapproximately constant temperature. That temperature, as I-have found,is a reliable indication of the performance of the furnace inpractically all cases, and is especially important in the case of openhearth furnaces operated at high temperatures, because the roof is theportion of the furnace most apt to fail as a result of over-heating, anda control preventing the attainment of a critical furnace roof heatcondition thus largely eliminates premature furnace failure `due toover-heating. A failure of the roof of such a furnace requires theshutting downof the furnace and a time consuming and expensive furnacerebuilding operation.- Maintenance of a higher and uniform average heatinput to the furnace is permitted by my automatic control asdistinguished from hand operation of the heat input with its attendantirregular fluctuations and consequent necessity for a Wide margin ofsafety. 'I'herefore with my automatic control, a faster melting timemay. be attained or, alternatively, a. larger refractory life. i In'thepractical use of that invention in controlling aregenerative open hearthfurnace in faccordance withhthe heat potential against the rooffI havefound that such acontrol tends ,to a desirable uniformity of operatingcondivgenerator operation results obtained are satisfactory andeliminate the necessity for frequently varying the periods between flowreversals in accordance with regenerator temperatures.

It has heretofore been proposed to insert thermocouplesV or other heatresponsive means in the roofs of furnaces either with or` withoutprotecting tubes but such devices are responsive to the temperature ofthe roof or some portion of it and accordingly are slow in responding totem-- perature changes in the furnace due to the high heat capacity orinertia of the roof. It is desirable for purposes of control and forpurposes of indicating fand recording in most cases, to obtain the rapidresponse made possible with my invention in order that a corrective stepmay be quickly taken .to check any undesirable trends. By theconstruction and arrangement of the device of my invention I render thethermocouple substantially heating effect to which furnace Walls androofs are subjected when heated over long peri'od's lof,"

time and thereby permit the immediate meas-- urement of the heatpotential on said vvall or roof.

For thel general purposes 'of' my novljcom' trol method, the heatpotential against the roof' may be measured by means of thel temperatureresponsive device of my invention, and my invention includes novelcooled thermocouple'con l tral or reducing character .of tlie combustionchamber atmosphere'which is made desirable by the particular conditionsof use. My improved control apparatus comprises novel and veffectiveprovisions for supplying fuel and air at suitably proportioned rates. ,AMy improved control-apparatus in its preferred form includesvarioushuid-'pressure con` trolled elementswhich are made subject to the tionsin thel two regenerator chambers, serving f master control of the heatpotential againstitlie roof, by means of a master controller tof knownor suitable type`creating5aruid lcontrol pressure which Aa function-of4.said temperature .con/diftion; -vf.. n ,i .Y t 1 y:The variousffeaturesf,of novelty characterizing the present invention arepointedfout. vlvitli4 independent of the cumulativev ticularity-in theclaims annexed to and forming a part ofl this specification. For abetter understanding of the invention, however, its advantages, andparticular objects obtained with its use, reference should be had to theaccompanying drawings and. descriptive matter in which I haveillustrated and described preferred forms of apparatus embodying andutilized in the practice of the invention.

Of the drawings: f

Fig. 1 is a diagrammatic representation of an open hearth furnacecontrol system;

-Fig. 2-is a sectional elevation of an open heart regenerative furnaceof conventional type having a water cooled thermocouple mounted in itscrown;

Fig. 3 is a sectional elevation on a larger scale than Fig. 2 of thewater cooled thermocouple.

In the embodiment of the invention illustrated in Figs. 1, 2, and 3, anopen hearth regenerative furnace A is supplied with combustion airthrough a conduit B, and with fuel through a conduit C. A reversingvalve BA is employed r to connectthe air supply conduit B to theregenerator inlet B' during periods which alternate with periods duringwhich the conduit B is connected to the other regenerator inlet B2. Areversing valve CA similarly connects the discharge en'd of the -fuelconduit C to a branch C opening at one side of the furnace combustionchamber A' during periods which alternate `with those during which theconduit C is connected to' a branch C2 opening to the opposite side ofthe combustion chamber. Areversing valve BA connects the outlet B fromone of the regenerators to a stack connection or olf-take flue D duringperiods in which combustion air is being suppliedV 7 common timecontrolled reversing mechanism E of any usual or suitable type. 1 Asdiagrammatically shownfthe reversing mechanism E includes separateoscillating Yoperating arms EB and EC for, and link connected to theoperating arms ofl the reversing valves BA and CA respectively.

When the fuel transmitted by the pipe C is' oil, it will ordinarily benecessary or desirable to employ atomizing burners, and steam supplyconnections including reversing valves for supplying vsteam to eachburner at times when that burner is receiving oil through thecorresponding fuel branch pipe C' or C2, but as said burners andconnections are Well known and form no part of the present invention,and are not needed when the fuel supplied by the pipe C is a gas, noillustration or further reference to such burners and steam supplyAconnections seems necessary herein.

The control system shown diagrammatically in Fig. 1, comprises a furnaceroof temperature responsive element F in the form of a thermocouplehaving its terminals connected by thermocouple leads I and 2 to theterminals of a mastercontrol instrument G. The latter receivescompressed air from a compressed air supply piping system 3, andoperates to maintain'an air in a pipe GH whichis determined by, and is afunction oi the thermocouple voltage impressed on the instrument G bythe conductors i and 2. The master control pressure transmitted from themaster controller G by the pipe GH is impressed on a regular .valve I-Iwhich regulates the fuel feed or now through the conduit C.

The regulator H is ofthe reaction type, comprising a flexible valveoperating diaphragm H' on one Aside of which is impressed the pressuretransmitted by' the pipe GH, while the opposite side of the diaphragm issubjected to a pressure transmitted to the regulator H by a pipe HI andconstituting a measure of the flow through the conduit C. The pressurein the conduit HI is determined by an element I which I call a staticconverter.- The element I includes a ilexible diaphragm I dividing apressure chamber into two compartments, one of which is connected by apipe I2 to the conduit C at the inlet, or upow, side of a restrictedmeasuring orifice C3 in the conduit. The compartment at the oppositeside of the diaphragm I' is connected by a pipe Ifx to the conduit C atthe outlet, or downflow side, of the measuring orifice C3. The element Iincludes a balancing pressure chamber I4, having its wall adjacent thediaphragm I formed by a flexible diaphragm connected to the diaphragm Iby a sternfor plunger element I5. The latter carries at one-end a valveI6 controlling the admission to the chamber I4 of compressed airsupplied by a branch of the compressed air supply pipe system 3. Througha restricted bleeder outlet I'l in a pipe connected to the chamber I4,air constantly escapes from said chamber to the atmosphere at a ratelower than that at which air is passed to the chamber by the valve I6 inthe wide open condition of the latter. The pipe HI is connected to thechamthe measuring orifice C3, and hen-ce is a measure of the flowthrough the conduit C. As 'will be apparent, the opposing actions of thepressures transmitted by the pipes GHand HI to the opposite sides of thediaphragm H of the regulator valve H, will normally maintain that valvein the adjustment required to balance those pressures, and thereby tomake the rate of flow through the conduit C a function of the mastercontrol pressure transmitted to the regulator H by the pipe GH.

The device K is a device, similar to the device I, creating aregulatorpressure force which is proportional to the difference betweenthe pressures at the inlet and outlet sides of a measuring orifice B3 inthe conduit B, and therefore is a measure of thev rate of now throughthe conduit B. The static converter K includes and has associated withit parts K-K7, respectively, corresponding to the above .mentioned partsI'-I". The measuring pressure chamber K4 of the element K is suppliedwith compressed air through a branch from the compressed air supplypiping 3, land the regulator pressure 'in the chamber K4 is transmittedby a pipe KJ to an element J.

The element J forms the motor pressure control valve element of anair-hydraulic regulator employed to adjust a damper L3 in the supplypipe B as yrequired tojmaintain such a rate of now through the conduitB, that the pressure in the measuring pressure chamber K4 of the elementK will be equal, or proportional to the pressure in the measuringpressure chamber I4'of the elej ment 1. This means, as is readilyapparent, that a constant proportion is maintained between the ows inthe conduits C and B, and

that the flow through the conduit B bears the same relation to' themaster control pressure in the pipe GH, asdoes the iiow through theconduit C. The ratio of the pressure in chamber Il to that in K4 may bevaried by a valve HJ which is placed in pipe HJ so as to reduce, ifnecessary, the pressure in HJ below the pressure in chamber I4 andthereby vary the ratio of the HOW in` Conduit C to that in conduit B.

As diagrammatically shown, Athe control ele,4 ment J includes a pressurechamber divided into two compartments by a flexible diaphragm J', thepipe KJ being connected to one, and the pipe y HJ to the other of thetwo compartments. The .central portion of the diaphragm J is connectedto, and gives movement to, a piston valve J2 which, in effect, is aD-valve working in a valve casing J3. The valve J2 serves in oneposition to connect a compressed air supply port .J4 to a port J5 in thevalve casing,while at` the same time permitting free flow through athird port` J6.

member J2 Vconnects the supply port J4 to the In a second and lowerposition, the valve port J5 and permits-free ow through the port J5.lThe port J4 is connected to a branch of the compressed air supplypiping 3.v The port J5 is connected by a conduit J'I to apressurechamber J9. The port Ji is connected by a pipe J8 to .a pressure chamberJ1.

The pressure chamber J9 is connected by a pipeJL to one end of thecylinder of a reciprocating hydraulic servo-motor L, and the vclriamberJ10 isy connected by a pipe JL' to the opposite end of that cylinder.servo-motor has its stem operatively connected The piston L' of the tothe operating arm L2 of a damper L5 in the pipe B, so that as the pistonL' is moved in one direction or the other, up or down as shown in Fig.l, the damper L2 is given an opening or closing adjustment: As indicatedinFig. 1, the cylinder of the servo-motor L, and the pipes JLandJL' arelled, and the pressure chambers J5 and J1 are partially filled by aliquid,

' y ordinarily oil, which is displaced as' required to eiect servo-motormovements, by compressed air cial provisions for mounting thethermocouple in the roof A2 over the combustion chamber A' Aof thefurnace A, and for cooling parts of 'the thermocouple structure andmounting which need to be cooled to prevent injurious over-heat-` ing.As shownin Fig. 3, the hot junction F' of the thermocouple isv imbeddedin a block F of carborundum` or analogous refractory material ofrelatively -good heat conductivity.

In the arrangement shown, the outer surface of the block ,Pris in theform of a section of a cone and is normally seated in the similarlyconical passage'f'- through the water cooled thermocouple mountingmember v;f. 'I'he latter is formed of metal and is provided with. ahollow wall or chamberspacelm through which circu.l `lates cooling watersupplied by a pipe M' anddischarged through a pipe M2. To prevent thedropping of the members `F and f and the connected water pipes into thefurnace in the event of collapse zof the roof, a chain suspension F'I Asupported at F'is .attached to member f in any suitablemanner. Themembers F or f need not be disturbed whengthe thermocouple proper isrmoved for thermocouple repair or replacement or for other purposes. y

, ln thearrangement yshown in Fig. 2, cooling water is supplied Vto thepipe M' through a branch from a vwater supplylfpipe M5, the branchincluding a pressure regulator M6 andhaving attached to it a pressuregage M'. A valved bypass Ms about the regulator Mi permits water to besupplied to the pipe M at times at which the -regulator M2 is subjectto. adjustment or rey pairs, or is otherwise inoperative. As shown theoutlet pipe M2 discharges into a waste or return connection M12. Inpractice, the thermocouple leads I and 2 shown in Fig. 1 are enclosed ina flexible cable F9 as shown in Figs. 2 and 3.

`In the operation. of the fluid cooled thermocouple arrangement, thecooling water or other a. condensation of the, gases surrounding the"supplied by the 'controlelement J to one or the I regulatingthespeedoflmovement f that piston in response to adjustments ofthe valveJ2,` and various other special features'of construction and arrangementwhichwas not, and ,n'qnot be i1- I maratea innig. 1, as they formappartenu@ fluid is passed through the member f at a rate sumcient towithdraw heat from the member F at approximately the rate at which'heatis supplied. `Thus the temperature responsive element is not subjectedto thecumulative heat effect or soaking" .condition of the furnace roof,to which the latterA is subjected after being heated for a period oftime. The rate of application of the cooling medium is, however,insuiilcient to cause member F. Such a condensation would result in theforming of slag thereby affecting the heat transfer relation and aconsequent undesirable eiect upon the calibrationof the measuringsystem.v I have found that with a volume of approximately-one quarter ofa cubic foot, thata quantity flow oi about ve cubic feet per minute issatisfactory.l f

For the general purposesyof vthe present invention, the mastercontroller G may be of any `usual or suitable formfadapted to` maintaina presentinventionfand are fully-disclosedfin the k patent`offAndrewJ.Fisher, Number 42,137,607, granted`Novemberr22,. 1938-, inwhich is, disclosed and claimed a preferred practical vform of anairfhydraulic regulator including the features illustrated in Fig. l andspecial'fea'tures. ,v Y, I

The thermocouple construction and arrangement illustrated in Figs. 2 and3, comprises. spethe aboveA mentioned master control'fluid pressureforce` 1n the pipe GHwhich is' a suitable*l predetermined function ofthe vtemperature to .which the thermocouple F fresponds, A,As showninFig.4 l; the controller G comprises ayolt meterhavingan element. G

which deflects counterclockwiseor clockwise, ac-

cordingly, vas a'fallor rise `in the heat potential against the.roofjdec'reases or'increases the thermocouple voltage transmittedto the`meter by the conductors landA 2; fAs-.diagrammatically shown, the pipeGH is connected to a conduit G2 receiving air from the compressed4 airsupply piping system 3 through a restricted orice G5, and

having an outlet port G4. Flow through the port G4, and thereby thepressure in the pipes Gr2 and GH, is regulated bya flapper valve Gadiusted by the deflection of the element G', as required to decrease orincrease the ow through the port G4 and thereby raise or -lower thepressure in the pipes G2 and GH as the heat potential against thefurnace roof decreases and increa-ses. AS diagrammatically shown, anadjusting device G is employed to adjust the position of .the port G4longitudinally of the path of deflection of the valve member G5, so thatthe heat potential against the roof which the control system tendsstrument has the abovementioned general characteristics of theinstrument G, and has special 'operative characteristics and structuralfeatures .which need not be illustrated or described herein.

The general mode of operation of the control apparatus illustratedherein hasbeen indicated in the foregoing description. With a suitableconstant, or approximately constant air pressure in the supply pipingsystem 3, the pressure maintained in the pipes G? and GH will dependupon the heat potential on the furnace roof to which the thermocouple Fresponds, and like the latter will be maintained approximately constantat values determined -by the adjustment of the adjusting device G6.pressed on the furnace roof falls below the normal value xed by anexisting adjustment of the device G6, the resultant deflection of themaster controller element'l G' will move the valve member G5 toward theoutlet G4 throttling the escape of air through the latter. Thisincreases .the pressure in the pipe G2 and gives an opening adjustmentto the fuel valve member regulator H. I'he device I and H cooperate aspreviously described tomake the increase in the fuel flow a function ofthe increase in the pressure transmitted to the device H by the pipe GH.The increased pressure in the pipe HI resulting from the increased flowin the conduit C which occurs on an -increase in the pressure in thepipe GH, is

transmitted through pipe HJ to the device J.

The latter then operates in conjunction with the device K to actuate theair-'hydraulic regulator L and adjust the valve L3 as required to so in.

considereda's an uninterrupted connection between element I7 andregulator J. I have found, however, that the addition of a connectionsuch as the connection I-IJ3 between the" supply conduit 3 and the pipeHJ affords an additional means f flexibility in operation whereby theregulator J may be loaded independently of the element I. 'Inserted inthe connection HJ3 is a When the heat potential imfurnace chamber A',which is practically im.v

portant in some cases. For example, in an openhearth furnace, it isordinarily quite important y theconverse of those described above asoccurring when the heat potential on the furnace-roof def,

creases.

As hereinbefore described, the conduit HJ was pressure regulator HJ-4,which is so adjusted that when the pressure in the line HJ falls below apredetermined minimum the' 4pressure regulator will act to admit fluidpressure from the fluid supply line 3 thereby maintaining the pressurein line HJ at said predetermined The pressure at which the regulatorHJ*l tends to maintain the pressure-in line HJ may be made below thelowest pressure maintained 1n line HJ as a result of the lowest normalfuel supply to which the differential staticconverter I is responsive sothat the regulator HJ* would come into play only when the fuel valve His entirely cut off. With, a fuel supply flowing through the line C atany rate normally called for by the.

regulator G, the regulator HJ* would therefore cut off connectionbetween the supply pipe 3 and the connection HJ.

In effect, therefore, the action ofthe regulator HJ4 Amay be made suchas to maintain a predetermined. minimum air flowA irrespective of thefuel cut off which may .occur as a result of the action of regulator Gwhen the temperature condition to which the latter is responsive dropsto a'predetermined minimum. The maintenance of a predetermined minimumair flow after the fuel has been appreciably reduced or cut off is ofconsiderable practical importance in some cases. Thus when the furnaceroof heat condition becomes dangerously high and the fuel supply rate isreduced or cut olf, the continuing flow of air through the combustionchamber of the furnace will result in a desirable reduction of furnacetemperature more quickly than can be reduced by merely reducing orcutting off the fuel supply. While the air then entering the combustionchamber -and wholly or' largely passing A not be preheated'to thetemperature then prevailing in the combustion chamber, and will absorbheat in that chamber and carry it out of the latter. The very fact thatthe air is preheated to a temperature approaching that in the furnacechamber before entering the latter, prevents the air from having achilling effect injurious to the furnace or its charge. Most of the heatcarried out of the furnace chamber by the excess air, is recoveredin theregenerative chamber then receiving the outflow of gases from theAfurnace chamber.

An important advantage of the apparatus of Fig. vv1, when thepredetermined air supply regulator HJ4 is employed, particularly inconnectionv with metallurgical or other furnaces in which analogousvreactions occur, arises from the chemical combination of the. excessoxygen supply, followingva fuel cutoff with carbon monoxide or othercombustibles liberated by the metal bath as the result of the meltingdown of a charge of metal. Such liberation of the combustible gases bythe bath is particularly pronounced at a time during the heat when itisdesirable to reduce the fuel supply and in ,the arrangement of Fig. 1Y

without 'the pressure regulatorHJ, a cessation of thelfuel supply wouldbe'accompanied by a 2,237,036 y cessation of the supply of combustionsupporting the roof of that chamber, have already been mentioned. Thespecial thermocouple construction illustrated in Figs. 2 and 3 not onlyprovides means responsive to the'sgnicant conditions and comprisesdesirable water cooling provisions to protect the thermocouple and itsmounting against dangerous over-heating, but is characterized by theease with which the portion of the thermocouple which needs to beinspected, repaired, and replaced, from time to time, may be removedwithout subjecting the furnace roof masonry to injury. As those skilledin the art will understand, there is some tendency for the masonry incontact with and immediately adjacent to the water cooled member f tocrack and spall. 'Ihe effect of the cracking and spallingis ordinarilynot at all serious if the mounting member f remains permanently seatedin the masonry, but might result in serious injury to the furnace roof,if it were necessary to remove and replace the member f from time totime.

While in accordance with the provisions of the statutes, I haveillustrated and described the best form of embodiment of my inventionnow known to me, it will be apparent to those skilled in the art thatchanges may be made in the form of the apparatus disclosed withoutdeparting .from the spirit of my invention as set forth in the ap-Dended claims and that in some cases certain features of my inventionmay be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent, is:

1. Means for measuring the temperature at the combustion chamber side ofa highly heated furnace combustion chamber` wall, comprising a watercooled mounting element mounted in said` wall, a block of refractorymounted in said element and composed of material having relatively highheat conductivity, a temperature responsive element mounted in saidblock and responsive to the temperature of the latter, and meansdeflected by said element.

2. Means for measuring the temperature at the combustion chamber side ofa highly heated furnace combustion chamber wall, comprising a watercooled mounting element mounted in said wall, a block of carborundummounted in said element, a temperature responsive means mounted in saidblock and responsive to the temperature of the latter, and'meansdeflected by said element.

3. Means for measuring the temperature at the combustion chamber side ofa highly heated' furnace combustion chamber wall comprising a block ofrefractory mounted in said wall and composed of material having arelatively high heat conductivity, a temperature responsive elementmounted in said block means for laterally withdrawing heat from saidblock at approximately the rate at which heat is supplied tosaid block,and means deflected by said element.

4. Means for measuring the temperature at the combustion'chamber side ofa highly heated furnace combustion chamber wall, said Wall beingresponsive to the cumulative effect of heat applied over an extendedperiod comprising a block of refractory mounted in said wall andcomposed of a material having a relatively high heat conductivity, a;temperature responsive element mounted in said block, cooling means formaintaining the heat condition of saidv block sufficiently differentfrom the heat condition existing in said furnace that minor fluctuationsin the operation of said cooling means is substantially ineffective.upon the magnitude of the response of said element, and means deflectedby said element.

5. Means for measuring a temperature which is a function of thetemperaturey of a heated chamber comprising, a chamber, apblock ofrefractory material of relatively high heat conductivity mounted in awall of said chamber, a temperature responsive element mounted withinsaid block, means deflected by said temperature responsive element,cooling means associated with said block for insulating said block fromthe heat condition existing in the wall of said chamber and alsobeing sooperated that minor fluctuations in the operation of the cooling meanscauses no substantial effect upon the operation of the deflected means.

' ANKER E. KROGH.

